1. Technical Field
The present invention relates to camper jack systems used to raise, lower and/or level a discrete body such as a camper body and, particularly, those types of camper bodies that rest in the bed of a pickup truck. More particularly, the present invention relates to a quick-release arrangement for use with a camper jack system that permits the jack leg to be released from a braked position such that the jack leg can be rapidly lowered to the ground when desired. The present invention also relates to a cooperating mechanical brake mechanism for use with the quick-release arrangement, when necessary or desired.
2. Background Information
Camper jacks are commonly used to raise, lower and support camper bodies and are especially prevalent with those types of camper bodies which rest in the bed of a pick-up truck. Typically, camper jack systems of this type have an outer housing portion which is permanently mounted at each corner of the camper body. Disposed within the housing is a jack leg which can be extended or retracted in a telescoping fashion by operation of the jack's lifting mechanism. When the camper body is to be removed from the truck, each of the jack legs are extended, first, to the ground and, then, further so as to lift the camper body from the bed of the truck. The truck can then be driven out from beneath the camper body that is now supported by the extended jack legs. When the camper body is to be mounted upon the truck bed, the process is reversed, resulting in the jack legs being retracted within the housing such that the jack legs are well above the ground to provide ground clearance for the truck during travel.
There are currently available a wide variety of camper jack implementations. Typically, a camper jack system generates a lifting force by way of an elongated screw and nut mechanism. The screw is threaded through the nut that is non-rotatably attached to the jack leg telescopically received within the jack housing. When the screw is rotated, the nut travels upwardly or downwardly along the screw, thereby causing the jack leg to be retracted or extended relative to the jack housing. Directional rotation of the screw to thereby either extend or retract the jack leg is typically effected by rotation of a drive shaft coupled either directly or through a gearing assembly to the screw above the nut. Rotation of the drive shaft is effected by a driving mechanism which can be manual and typically comprises a hand cranking system, or can be powered, as by a hydraulic system or a power motor system, typically a battery-operated electric motor.
When the camper body is not in use, it is desirable for the jack legs to remain safely retracted within the jack housing. Moreover, when the truck carrying the camper body is travelling, it is essential that the jack legs remain retracted within the jack housings. An extended jack leg presents a very dangerous situation because it can catch upon the ground or some other object and result in damage not only to the camper jack system but also to the camper body, the truck and, worst of all, people in the vicinity and/or within the truck. Accordingly, it is desirable to have some means for safely locking each jack leg in the retracted position. On the other hand, when it is desired to extend the jack legs, the process of extending the jack legs to the ground is relatively time-consuming. Thus, it has been considered desirable to have some means for releasing each jack leg in a manner that permits rapid extension of the jack leg to the ground.
Both of these objectives have been addressed with various types of releasable locking means that rely on some type of latch having a notch and engaging pin arrangement. For example, U.S. Pat. No. 5,273,256 issued to Chambers, the entire disclosure of which is hereby incorporated herein by reference, discloses a releasable locking means for a manually-driven camper jack system which uses a low friction ball screw threaded through a ball nut that is non-rotatably attached to the jack leg telescopically received within the jack housing for extending and retracting the jack leg. The releasable locking means comprises a latch positioned within a sleeve wherein the sleeve protrudes from the gear assembly housing and surrounds a crankable shaft adapted to be telescoped within and coupled to a driving portion of a hand crank. The crankable shaft is coupled through the gear assembly to a second shaft coupled to the ball screw. The latch includes a collar which is slidably mounted on the crankable shaft and has radially extending and diametrically spaced ears which protrude through a corresponding pair of slots in the sleeve. The collar is formed with notches to receive a key in the form of an engaging pin extending radially through the crankable shaft. A spring is used to normally urge the engagement of the notches on the collar with the engaging pin to thereby prevent rotation of the crankable shaft and thereby lock the jack leg in the retracted position. To release the lock, the collar is slid along the crankable shaft in the direction of the spring such that the notches are disengaged from the engaging pin to thereby free the crankable shaft for rotation. By virtue of the low friction between the ball nut and ball screw, pushing downwardly on the base of the jack leg permits the ball screw, coupled to the freely rotatable crankable shaft, to freely rotate and rapidly lower the jack leg to the ground. To hold the collar in the unlocked position, a second pair of slots, slightly wider than the first pair, are formed on the sleeve immediately adjacent the first pair such that axially facing shoulders or detent surfaces are formed at the junction of each wide slot and each narrower slot. As the collar is slid along the crankable shaft in the direction of the spring, the ears are turned to engage the detent surfaces and thereby hold the collar in the unlocked position. An additional feature is an "automatic" release of the latch effected by placement of the driving portion of the hand crank in position to begin the cranking operation. As the driving portion of the hand crank is slid over the crankable shaft and coupled thereto, the driving portion contacts the collar within the sleeve and slides the collar toward the spring thereby disengaging the notches on the collar from the engaging pin and, thus, freeing the crankable shaft and screw for rotation. At this point, the jack leg can be rapidly lowered to the ground while the crank handle correspondingly freely rotates.
It will be appreciated that the mechanics of the above-described releasable locking means are relatively complex and require multiple interacting components. Both of these factors increase the cost and difficulty of manufacturing the releasable locking means and also may decrease the reliability and durability of the camper jack system. In addition, because the releasable locking means are automatically unlocked when the crank handle is inserted and thereby moves the latch notch out of engagement with the engaging pin, inadvertent release of a jack leg can occur when a person, e.g., a person unfamiliar with the arrangement, an inexperienced or, even, an experienced but inattentive person, inserts the crank handle without intending to release the jack leg. Another problem is that, because the crank handle is inserted against the spring bias force of the releasable locking means, it is necessary to continually apply pressure to keep the crank handle engaged and the lock released. If sufficient pressure is not applied, the crank handle is pushed outwardly by the spring and the lock "automatically" becomes re-engaged such that the entire maneuver of inserting the crank handle to release the lock must be repeated before the process of lowering of the jack leg to the ground can resume. Rather than permitting a simple, smooth and continuous lowering of the jack leg to the ground, the lowering process proceeds intermittently with cumbersome and annoying multiple repetitions of the lock release maneuver.
Other types of releasable locking means do not provide for automatic unlocking but, instead, require a separate manual operation to disengage the engaging pin from the latch notch. In these cases, however, cranking or otherwise operating the jack's lifting mechanism without first performing the manual unlocking operation to disengage the engaging pin from the latch notch can result in damage to one or more of the components of the camper jack system, e.g., shearing, bending, or otherwise breaking of either or both the engaging pin and the latch notch and/or damage to the lifting mechanism or other components of the camper jack system and may even result in injury to a person in the vicinity.
Another problem with known releasable locking means that rely on some type of latch having a notch and engaging pin arrangement is that inadvertent release of a jack leg can occur due to vibration and/or sudden jolts or jars to the camper jack system and, in particular, due to the vibration, bumping, and bouncing that occurs during travel of the truck, that unlocks the releasable locking means by causing disengagement of the latch notch and the engaging pin. As described previously, extension of a jack leg during travel of the truck is very dangerous and can result in damage not only to the camper jack system but also to the camper body, the truck and, worst of all, people in the vicinity and/or within the truck.
Accordingly, disadvantages of known releasable locking means that rely on some type of latch having a notch and engaging pin arrangement include the relatively complex mechanics requiring numerous interacting components, the need to repeat the automatic release maneuver, the possibility of damage and/or injury when the jack's lifting mechanism is operated without first releasing the locking means and the hazards related to inadvertent release of the jack leg and, particularly, inadvertent release caused by vibrations or jolts or jars during travel of the truck.
In view of the foregoing, it would be an advance to provide a simple, reliable, durable, and safe quick-release arrangement for a camper jack system that permits the jack legs to be released from a brake control such that the jack legs can be rapidly lowered to the ground. It would be a particular advance to provide a simple, reliable, durable, and safe quick-release arrangement for a camper jack system that is resistant to inadvertent release due to normal vibration and jolting and jarring and, especially, vibration and bouncing and bumping that occurs during travel of the truck equipped with the camper jack system. Another advance would be provided by a quick-release arrangement that is safe even in situations where an operator fails to properly engage or disengage the quick-release arrangement before operating the motor, or other driving mechanism, such that damage to the quick-release arrangement, the driving mechanism or other components of the camper jack system and/or injury to persons in the vicinity are prevented. It would also be an advance to provide such a quick-release arrangement that is mechanically simple and requires few interacting components and, thus, is relatively inexpensive and easy to manufacture.
Motorized camper jack systems have an inherent brake mechanism in that the motor is selectively operable in the forward and reverse directions and does not permit movement of the drive shaft in an opposite direction to the motor's directional setting. Thus, the motor's resistance to opposing movement acts as a brake to prevent the jack's lifting mechanism from operating in reverse until and unless such reverse operation is desired. In motorized camper jack systems it may be desired, and in non-motorized camper jack systems it is necessary, to have a brake mechanism to lock the jack leg in a retracted position. It will be appreciated that it would also be an advance to provide a cooperating mechanical brake mechanism for use with a quick-release arrangement, when necessary or desired.